Minutes of the
Jefferson Lab CLAS Collaboration
January (25-27), 2001
Next meeting: June 7 - 9, 2001 at Jefferson Lab, CEBAF Center
For you to do:
1) If you are the spokesperson for an official experiment, or if you
are doing an individual analysis of CLAS data, finish your Annual
Progress report for the laboratory by February 5th. The template is
attached at the end of these minutes. See below for details.
2) Save the dates for the next CLAS meeting, given above.
________________________________________________________________________
About 80 members of the CLAS Collaboration met for the
three-day winter meeting at CEBAF Center. CLAS is in the midst of a
very productive and long run of the eg1(2000) experiment, running with
high polarization electron beams on polarized NH3 and ND3 targets.
There have been no major breakdowns of Hall B equipment since the last
meeting.
Here are some numbers that characterize where we are: Since
the last meeting in September, one publication (our first) has a
appeared in PRL, another has been accepted by PRL, and one has been
submitted to PRC. All of these physics publications are available on
our web site. Three instrumentation (NIM) papers were accepted since
the last meeting. During the meeting we counted ten physics analyses
that are approaching the publication stage, meaning that they will be
submitted (or be close to submission) by the time we meet again in
June. The Collaboration has 82 identified analysis projects, most of
them with data in-hand to work with, 47 graduate students, 8 completed
PhDs, and there are 10 post-doctoral researchers on site from outside
user groups. When the eg1 runs end in April the CLAS program will
have used 267 of 405 days of approved beam time since data-taking
began.
Jeopardy Review
---------------
The Hall B program will face its first beam time jeopardy
review by the PAC in July of this year. The purpose of this review is
to justify the remaining beam time in the program in light of
developments in the field. A plan for how this will be done was
presented by the Chairman for Collaboration input. The plan was
worked out among Larry Cardman, Bernhard Mecking, Reinhard Schumacher,
and several other people. Since CLAS experiments are mostly organized
by "run groups", the review will be by run groups. Stand-alone
experiments will be reviewed individually. Hall B does NOT have the
very large backlog of experiments that the other halls had; depending
on some of the counting details, we presently have between a 2.5 to 3
year backlog. Larry Cardman has decided that ALL of the beam time
that comes up for jeopardy review MAY be re-approved on scientific
merit. This is true as long as the PAC is not inundated with new beam
time requests. The operative formula for the summer PAC will be that
"100% + 45 days" is available for distribution.
The plan calls for the jeopardy review to be split into two
sessions, PAC 20 in July '01 and PAC 21 in January '02. In the first
round the review will include several specialized-setup experiments:
eg1/photon: 91-015 Helicity Structure of Pion Photoproduction
g7/94-002 Protoproduction of Vector Mesons off Nuclei
e1/93-043: Measurement of the Delta-Delta Component of the
Deuteron by Exclusive Quasielastic Electron Scattering
e6/94-102, 94-019 (Deuteron experiments) (may be on '02
schedule in time to excape review)
In addition, the entire e1 program (run group) would be
reviewed. The second round of experiments would include g1, g2, and
g3. The PAC will not review experiments that are on a run schedule
and are scheduled for their complete remaining time. It remains to be
determined whether the e2, the e6 deuteron experiments, or the g2 and
g3 experiments will be on the tentative 2002 schedules in time to
avoid this review. Also, the PAC will not review experiments whose
beamtime has been completed previously, which includes eg1/electron,
g5, e5, and g6.
The PAC presentations for the run groups will include an
overview talk which highlights accomplishments of the run group,
especially those analysis efforts which will not give detailed
presentations. Then one or two "lead" experiments will motivate the
need for the additional beam time. The run groups will be allowed to
ask that their remaining beam time be redirected to updated running
conditions They can also ask for additional beam time, but since this
affects the whole CLAS program, requests for additional beam time must
first be proposed and approved by the Collaboration.
The run groups were asked at this meeting to identify their
coordinators for this review. The e1 group appointed V. Burkert,
P. Stoler, L. Elouradrhiri, D. Carman, and R. Minehart to this job.
The g1 group will have W. Briscoe coordinating the work. The g2 group
will have P. Rossi in charge. The g3 group will have B. Berman in
charge.
Annual Reports
--------------
The Lab have asked all Spokespersons to submit a multi-page
annual report contributions on their work. We decided to appoint CLAS
members to write overview descriptions of the run groups. This is to
avoid redundancy in the individual contributions from the members.
These persons should also act as editors to streamline, as needed, the
contributions. The appointees are:
e1 Volker Burkert
e2 Stepan Stepanyan & Larry Weinstein
e5 Mike Vineyard
eg1 Sebastian Kuhn
g1 Bill Briscoe
g2 Patrizia Rossi
g3 Barry Berman
g5 Barry Berman
g6 Jean Marc Laget
g8 Phil Cole
These people are only writing the OVERVIEWS. Each member who is doing
an analysis is asked to write up a summary of his or her analysis
project. This is not restricted to "official" experiments only. Any
CLAS analysis effort, whether "individual" or "CLAS Approved
Analysis", or even projects pending beam-time are asked to write a
short report.
Please put your contribution in the CLAS secure web-site directory
under your run group's heading, or e-mail it directly to the relevant
person above (if your postscript figures won't gag his or her email
system). Recall that the Latex template were were asked to use was
sent to us on December 22nd. [I have attached a copy to the end of
these minutes in case you didn't get one.]
Do this by February 5th.
[I trust the persons listed above will submit the consolidated results
to the Lab by the deadline one week later.]
CLAS Approved Analysis
----------------------
At this meeting the Collaboration heard, discussed, and voted
on three proposals for "CLAS-Approved Analyses". These were the first
proposals to undergo CLAS internal review and vote under our CAA
policy. Recall that the purpose of CAA's is to establish formal
recognition of an analysis project that will not go before the PAC
because it is based upon already-taken data. It allows collaborators
to demonstrate that they have the support of the whole group, which
may be important in their efforts to attract funding or students. At
this meeting we heard three CAA proposals:
S. Stepanyan Deep Virtual Compton Scattering at 4 to 5 GeV Using
CLAS
J. Kellie Photoproduction of Associated Strangeness
using a Linearly Polarized Beam of Photons
N. Pivnyuk Production of hadronic systems near
threshold in eA interactions at high momentum transfer
Each of these proposal was voted upon by full and term members by
secret ballot. They all were passed by the necessary 2/3 majority.
Other Notes
-----------
Dennis Weygand presented a request which will be made to the
PAC next week for an extension of the g6/99-005 beam time of 6 days.
This would bring the total time to 10 days. Combined with improved
beam intensity, torus setting and DAQ performance, the run would net
about 10 times more data than now exist for meson searches. By hand
vote, the extension was approved as a full CLAS effort: ~40 yea, ~0
nay, ~4 abstain.
In the plenary sessions, very interesting physics talks on
advanced analyses were given by John Price, Cole Smith, Kyungseon Joo,
Steve Barrow, Marco Ripani, Bin Zhang, Matthieu Guillo, Robert
Feuerbach, John McNabb, Ken Hicks, and Alex Stavinskiy. [These talks
will not be recounted or summarized here: there was so much
information in these talks it is impossible to capture fairly, and
these minutes are long enough already!
There are several drafts of papers in the pipeline for
publication. The Collaboration may expect more calls from the
Chairman and/or the Working Group leaders in the next few weeks and
months with requests that people serve on review committees. [We note
that the SoN and the Real Photon working groups have decided to
approve analysis results using appointed subcommittees to probe the
details of a given work. These Working Group subcommittees are NOT
replacements of the Collaboration-wide Ad Hoc committees that are
appointed by the CCC. Thus, we have evolved into a structure where
each paper is being reviewed twice, essentially, before it goes to the
full Collaboration for comments. Note that these reviews are not
intended to be private or exclusionary. If you want to help out, feel
free to volunteer. The process we have is intended to reduce the
total workload on the Collaboration.]
Hardware, Software, Infrastructure
----------------------------------
Dieter Cords reported on continuing impressive gains in
performance of the Data Acquisition system. It now can acquire data
up to about 4000/sec (up from about 3000/sec) with a smooth dead-time
behavior as a function of rate. The newest improvements were made
possible by "microprogramming" the SFIs such that the front-end
readout time was reduced from 250 microseconds to 100 microseconds.
This work was done largely by Vardan Gyurjyan. The present limit in
the system the rate of writing data to disk, at about 24 Mbyte/sec.
Also, there is now a more sophisticated and faster structure for
on-line event filtering and reconstruction, for things like monitoring
the target polarization from actual scattering data.
Mark Ito discussed the offline situation. There are now 125
nodes on the farm. The farm has been idle for data cooking some time,
but via the introduction of a new lower-priority queue it has been
used to generate GSIM data for the e2 group.
A big change-over to the new calibration database (Cal DB) was
presented. This new database structure will replace the Map Manager
that has been used for the last three years. The new Cal BD will be
the calibration database of record starting MONDAY January 29th. The
official Map will be copied over into the Cal DB and then made
"readonly". Users of the cooking codes will have to relink their
codes using new libraries which will transparently change all Map
calls to Cal DB calls. Conversion scripts like "map2db.pl" and
"db2map.pl" are available for people who want to continue working with
private copies of the Map Manager for the time being.
There seems to be a mind-boggling about of disk-space
available now. Mark introduced the notion of DST disks which are
permanent storage space for up to 6 Terabytes (lab wide?) of DST data.
He proposed that each CLAS run group that requests it may get 200 Gb
of space.
Mark advocated revisiting the issue of offline code
management. He pointed out that run groups manage their own affairs,
but the calibration and cooking software that they have in common is
not being managed by anyone with designated responsibility or
authority. This has led to fragmentation of codes and lowered
efficiency in the calibration and cooking of CLAS data sets. The
documentation is out of date, and the codes are hard to use. Expert
knowledge is lost when certain graduate students or staff move on to
new jobs. Suffice it to say that many opinions were aired. It is
fair to say that there is indeed a problem with our offline code
organization, but the real issue is what can be done to solve the
problem. These questions were again brought up for discussion on
Saturday afternoon as part of the Coordinating Committee report, where
once again many opinions were aired. Discussions are sure to
continue.
Mac Mestayer reported on two items in "tracking distortions"
due to magnetic field and/or alignment. Studies of how the magnetic
field model affects data quality have led to the adoption by g1c of a
hybrid field map which is 67% "new" (computed using the improved coil
geometry) and 33% "old" (what every run period has used for cooking up
to the present time). This work was done by a number of people
including Gordon Mutchler and Eugene Pasyuk. In Gordon's case, he
studied the reconstructed hyperon mass as a function of angle to find
the "best" field mixture. It was in rough agreement with what Mac
found with Konstantin when looking at reconstructed beam momentum via
two methods. Eugene found that a larger number of tracks were found
by time-based tracking with the improved field map: in the
neighborhood of 4% for negative hadron tracks. Most of the gains were
at the edges of the acceptance in theta and phi, but they also showed
a slight unexplained phi dependence. Volker Burkert warned that the
improved field has not been studied carefully for electron tracks.
Peter Heimberg reported in photon normalization issues. He
concluded that most data sets have run-to-run normalization
consistency at the level of 2-3%, while the absolute normalization
uncertainty ranges at the present time from 2% (g5) to 20% (g2).
Arne Freyberger reported on new beamline instrumentation,
especially related to monitoring the helicity-dependent charge
integrals seen by the experiments. There are now four monitors of
beam intensity: (1) a synchrotron light monitor at the bend into the
hall. This is very stable and tracks the Faraday cup with very good
linearity. It will be useful to use this as a flux monitor during
photon runs. (2) (3) There are two Optical Transition Radiation
detectors which look at backward light scattering from a 0.8 micron
aluminum foil which sits in the beam. One is used only for Moeller
runs. The other also tracks the Faraday cup very well. (4) The
Faraday cup has improved electronics so it can integrate the beam flux
at the 30 Hz rate at which the helicity flips. It is calibrated so
that one "count" corresponds to 675k electrons (!).
Run Status Updates
------------------
Sebastian Kuhn reported on the eg1 run which is in progress.
Compared to the first eg1 run, the target polarizations have been
better, as has the rastering of the beam on target. He showed
impressive results of the first-ever measurement of quasi-free
scattering of electrons from a pure Nitrogen-15 target which showed
clear differences relative to a carbon target, especially in the
higher W region. This is important for doing background subtraction
or dilution-factor calculations for the NH3 or ND3 runs.
Dan Sober discussed the recently-organized measurement of the
GDH sum-rule asymmetry in the 2.5 to 4 GeV energy range. The
measurement would fill a gap between the soon-to-be-taken data at Bonn
and SLAC. It is believed that CLAS, which was not designed as a
'total cross section measurer' can nevertheless capture about 85% of
the total hadronic cross section. This few-day run was in progress
during this collaboration meeting.
Dave Tedeschi reported on the readiness of the g8 group to run
using a LINEARLY polarized photon beam created using coherent
bremsstrahlung. The goniometer has been tested and works, and the
(optional) pair polarimeter has also been tested and shown to work; it
will be calibrated at Spring-8 in Japan in two months.
Volker Burkert reported on preparations for the e1 run at 6
GeV. Run conditions were reviewed. The main open question in whether
it would help to move the target on CLAS upstream by roughly 1 meter,
for which the acceptance for various channels would increase by a
factor of 2. Studies of Moeller background and tracking issues are in
progress.
Luminita Todor declared that the Pass_1 cooking of the g1c
data set has begun. She showed a number of graphs that showed the
excellent quality of the data.
Ken Hicks showed some plots of the status of the e1d
calibrations. Lots of work remains, but progress is being made.
On Saturday the Chairpersons of the Physics Working Groups
gave summaries of the PWG meetings; we will not summarize the
summaries here.
Membership
----------
We are pleased to welcome Harout Avakian into his new role as
Hall B postdoctoral research staffer. Harout was formerly working for
the Frascati group, and will now be working with Mark Ito on offline
software issues.
The full membership application for Franz Klein, former JLab
staff person and now Assistant professor at Florida International
University, was presented by Kevin Giovanetti. Franz is deeply
involved with the g8 (linearly polarized photons) run group, as well
as the omega analysis. A vote was held and Franz was elected as a full
member. [Congratulations Franz, we can't live without you.]
Kevin Giovanetti discussed database issues related to the CLAS
authorship lists. We now have a stabilized system for generating the
starting author lists for any given run period.
Talks
-----
Jean-Marc Laget, chairman of the CLAS Speaker Committee,
reported on recent trends in invited and contributed talks. A total
of 115 invited and contributed talks have been given by a total of 60
speakers. We saw that the CSC is actively soliciting CLAS talks at
major conferences and at APS meetings. We were reminded that all talk
invitations to conferences must be given to the CSC for approval, and
that the procedure for doing this is well documented on the web page
maintained by the CSC.
The main meeting adjourned at about 5:30 on Saturday with about 30
tough survivors still in the room.
Any changes, additions or other clarifications of these minutes by the
Collaboration members will be cheerfully considered. Amended minutes
will be sent out only in case of egregious errors or omissions.
[...]=chairman's editorials
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